Megaselia romoensis n. sp.

(Figs 183–198)

Diagnosis. In the key of Lundbeck (1922) for Group VII it runs to couplets 27 and 28, but none of the options fit. In the key to the males of the British species (Disney, 1989) it runs to couplets195 lead 1 M. tarsella (Lundbeck) and 253 lead 2 M. uliginosa (Wood). The costal index of both species exceeds 0.46 and they differ in their hypopygia and other details. Subsequent additions are also ruled out. In Borgmeier’s (1966) key to Nearctic Group VIII it runs to couplet 10 lead 1 to his misidentified M. bovista (Gimmerthal), see above under M. falloclavis n. sp. Of this confusion of species only M. abdita Schmitz needs consideration here. It is readily distinguished by its hypopygium, brown Haltere and the hairs below the basal half of the hind femur being shorter than those of the anteroventral half. Our species fails to run to any species in the rest of the world’s fauna. Apart from other details a distinctive feature that excludes most species is segment 5 of the mid tarsus being about 1.3 times longer than segment 4. Most species of Megaselia have segment 4 longer than 5. The subcosta of our species appears to end before reaching vein R 1 in one focus but seems to reach it in another focus (cf Figs 197–198). However, where the distinction is used in the key to British species at couplet 187 a note adds that variable species are keyed both ways. Indeed both routes lead to M. tarsella (see above).

Description. Male. Frons as Fig. 183, with microtrichia restricted to margins. Cheek with 4 bristles and jowl with 2 that are much longer and more robust. Postpedicels pale brown, without SPS vesicles (Fig. 185), and as Fig. 184. Palps and proboscis as Fig. 184, the labella with only a few short spinules below. Thorax brown, with 3 notopleural bristles and no cleft in front of these, and mesopleuron bare (Fig. 186). Scutellum with an anterior pair of small hairs and a posterior pair of bristles (Fig. 187). Abdomen as Fig. 188, the pale venter with hairs on segments 3–6. Hypopygium as Figs 189–191, there being no right hypandrial lobe and the cerci being 2.4–2.5 times as long as their breadths. Legs yellowish to even paler. Fore tarsus with posterodorsal hair palisade on segments 1–5 and as Figs 192 and 193. Dorsal hair palisade of mid tibia extends about 79 times its length. Mid tarsus with segment 5 about 1.3 times the length of 4 (Fig. 194). Hairs below basal half of hind femur longer than those of anteroventral row of outer half (Fig. 195). Hind tibia with a dozen robust differentiated posterodorsal hairs (Fig. 195), without anterodorsals, and spinules of apical combs simple. Wings (Fig. 242) 1.8–1.9 mm long. Costal index 0.40–0.42. Costal ratios 4.8: 1.6: 1. Costal cilia (of section 3) 0.12 mm long. Vein 3 hair 0.03 mm long. 3 axillary bristles, the outermost being 0.17 mm long. Sc not reaching R1 or just reaching R1, depending on the focus (Figs 197 & 198). Haltere knob pale (Fig. 196).

Type material. Holotype male, DENMARK, DK SJ, Rømø Sønderland, grassland, 11–30.VII.2017, Esben Bøggild (UCMZ —9–17).

Etymology. Named for the type locality tof Rømø in The Wadden Sea.